In a number of biological substance-turnover or substance-producing processes of various kinds, bubbles of air or other gas are introduced into or emerge in a usually aqueous liquid.
In some situations, the limiting factor for the turnover or production process is the removal of used bubbles.
This situation is known from the European patent EP 0 510 010, in which a centrifugal separator built into the loop of a loop reactor is used to carry out a complete or partial removal of the bubbles from the reaction liquid.
In other situations, the limiting factor for the turnover or production process is the oxygen consumption capacity of the liquid itself.
This may be the case in conventional use of activated sludge for treatment of water.
Treatment of water using activated sludge may be carried out using alternating periods of aeration and no aeration. Through this, nitrification of ammonium, nitrite, and organically bound nitrogen can be achieved in periods of aeration, whereas denitrification of nitrate and possible nitrite to gaseous nitrogen can be achieved in periods of no aeration.
The disadvantage to such an alternation between periods of aeration and periods of no aeration is that this—in conventional use of the activated sludge—is a slow process, measured as degree of achieved treatment per cubic meter of water per hour.